1. Field of the Invention
This application is directed toward fire-rated wall construction components for use in building construction.
2. Description of the Related Art
Header tracks, including slotted header tracks, are commonly used in the construction industry as a portion of a wall assembly. A typical header track resembles a generally U-shaped (or some other similarly shaped) elongated channel capable of receiving or covering the ends of wall studs and holding the wall studs in place. The header track also permits the wall assembly to be coupled to an upper horizontal support structure, such as a ceiling, floor of a higher level floor of a multi-level building, or a support beam.
Header tracks generally have a web and at least one flange extending from the web. Typically, the header track includes a pair of flanges, which extend in the same direction from opposing edges of the web. Along the flanges of the slotted tracks generally is a plurality of slots. When the wall studs are placed into a slotted track, the plurality of slots accommodates fasteners to permit attachment of the wall studs to the slotted track. The slots allow the wall studs to move generally orthogonally relative to the track. In those areas of the world where earthquakes are common, movement of the wall studs is important. If the wall studs are rigidly attached to the slotted track and not allowed to move freely in at least one direction, the stability of the wall and the building might be compromised. With the plurality of slots, the wall studs are free to move. Even in locations in which earthquakes are not common, movement between the studs and the header track can be desirable to accommodate movement of the building structure due to other loads, such as stationary or moving overhead loads, for example.
Fire-rated wall construction components and assemblies are also commonly used in the construction industry. These components and assemblies are aimed at preventing fire, heat, and smoke from leaving one portion of a building or room and entering another, usually through vents, joints in walls, or other openings. The components often incorporate fire-retardant materials which substantially block the path of the fire, heat, or smoke for at least some period of time. Intumescent materials work well for this purpose, since they swell and char when exposed to flames, helping to create a barrier to the fire, heat, and/or smoke.
One example of a fire-rated wall construction component is a head-of-wall fire block device sold under the trademark Firestik®. The Firestik® fire block product incorporates a metal profile with a layer of intumescent material on its inner surface. The metal profile of the Firestik® fire block product is independently and rigidly attached to a wall component, such as the bottom of a floor or ceiling, and placed adjacent to the gap between the wallboard (e.g., drywall) and the ceiling. The intumescent material, which is adhered to the inner surface of the metal profile, faces the wallboard, stud and header track. The space created in between the wallboard and ceiling, and the space between the stud and header track, allows for independent vertical movement of the stud in the header track when no fire is present.
When temperatures rise, the intumescent material on the Firestik® fire block product expands rapidly. This expansion creates a barrier which fills the head-of-wall gap and substantially inhibits or at least substantially prevents fire, heat, and smoke from moving through the spaces around the stud and track and entering an adjacent room for at least some period of time.
Some fire-retardant wall systems include a header track that incorporates a fire-retardant material directly on the header track. For example, a header track sold by California Expanded Metal Products Company d/b/a CEMCO, the assignee of the present application, under the trade name FAS Track® includes intumescent material applied to the header track. Preferably, the track is configured to at least substantially prevent the passage of air through a head-of-wall gap in conditions prior to any expansion of a heat-activated expandable fire-retardant material or prior to complete expansion or expansion of the heat-activated expandable fire-retardant material sufficient enough to close the head-of-wall gap.